1. Field of the Invention
The invention relates to wet extraction wherein cleaning fluid is delivered to a surface to be cleaned and the cleaning fluid is removed from the surface to be cleaned by suction. In one aspect, the invention relates to reducing suction from a suction nozzle to lengthen the dwell time for applied cleaning solution to a surface. In another of its aspects, the invention relates to a method for selectively lengthening the dwell time for cleaning solution that has been applied to a surface in an extraction process.
2. Description of the Related Arts
Extractors are well-known devices for deep cleaning carpets and other fabric surfaces, such as upholstery. Most carpet extractors comprise a fluid delivery system and a fluid recovery system. The fluid delivery system typically includes one or more fluid supply tanks for storing a supply of cleaning fluid, a fluid distributor for applying the cleaning fluid to the surface to be cleaned, and a fluid supply conduit for delivering the cleaning fluid from the fluid supply tank to the fluid distributor. The fluid recovery system typically comprises a recovery tank, a nozzle adjacent the surface to be cleaned and in fluid communication with the recovery tank through a working air conduit, and a suction source in fluid communication with the working air conduit to draw the cleaning fluid from the surface to be cleaned and through the nozzle and the working air conduit to the recovery tank. Examples of extractors are disclosed in commonly assigned U.S. Pat. No. 6,131,237 to Kasper et al. and U.S. Pat. No. 6,658,692 to Lenkiewicz, which are incorporated herein by reference in their entirety. Vacuum cleaners are also well-known cleaning devices for cleaning a range of items including carpets and drapery. Historically vacuums included a suction-relief vent for reducing the suction power to a suction nozzle.
U.S. Pat. No. 6,662,402 to Giddings et al. discloses a soil transfer extraction cleaning method employing a roller assembly including a soil transfer cleaning medium to mechanically remove soil from the surface to be cleaned. The method includes the steps of successively and repeatedly wetting a portion of the cleaning medium with a cleaning liquid, extracting any soil and at least some of the cleaning liquid from the previously wetted portion of the cleaning medium, and wiping the surface to be cleaned with the cleaning medium so as to transfer soil from the surface to be cleaned to the cleaning medium.
U.S. Pat. No. 6,735,812 to Hekman et al. discloses an apparatus having a cleaning implement in selective wiping contact with the surface to be cleaned; a cleaning solution dispenser that selectively wets a portion of the cleaning implement, a portion of the surface to be cleaned, or both; a first selectively controllable vacuum extractor tool to remove some of the dispensed cleaning solution and soil from the cleaning implement; and a second selectively controllable vacuum extractor tool which removes soil and some of the cleaning solution directly from the surface to be cleaned.
Traditionally, carpet extractors deliver cleaning fluid directly to a surface to be cleaned or onto an agitation system that subsequently delivers the cleaning solution to the surface to be cleaned. In both cases, the surface to be cleaned is saturated with cleaning fluid and allowed to dwell a sufficient amount of time in order to maximize the efficiency of the chemical process. In a second step, the cleaning solution together with any entrained debris is removed from the surface to be cleaned and collected via the fluid recovery system. In some cases it is desirable to increase the dwell time for portions of a carpet that are especially soiled.